Systems and methods for substituting virtual dental appliances

ABSTRACT

Systems and methods are disclosed for performing virtual treatment using one or more dental appliances by receiving a digital model of a dental appliance; selecting a standard position and orientation; and mapping the digital model of the dental appliance to the standard position and orientation.

PRIORITY DATA

This application is a continuation of U.S. patent application Ser. No.10/981,855 filed Nov. 5, 2004, the full disclosure of which isincorporated herein by reference.

BACKGROUND

The invention relates generally to computer-automated development of anorthodontic treatment and appliance. Orthodontics is the branch ofdentistry that deals with the straightening of crooked teeth. Althoughthere are many types of appliances that can be used by an orthodontistto straighten the teeth, the most common appliance is braces. Bracesinclude a variety of appliances such as brackets, archwires, ligatures,and O-rings, and attaching braces to a patient's teeth is a tedious andtime consuming enterprise requiring many meetings with the treatingorthodontist. Consequently, conventional orthodontic treatment limits anorthodontist's patient capacity and makes orthodontic treatment quiteexpensive.

Before fastening braces to a patient's teeth, at least one appointmentis typically scheduled with the orthodontist, dentist, and/or X-raylaboratory so that X-rays and photographs of the patient's teeth and jawstructure can be taken. Also during this preliminary meeting, orpossibly at a later meeting, an alginate mold of the patient's teeth istypically made. This mold provides a model of the patient's teeth thatthe orthodontist uses in conjunction with the X-rays and photographs toformulate a treatment strategy. The orthodontist then typicallyschedules one or more appointments during which braces will be attachedto the patient's teeth.

Historically, the practice of orthodontics has been a manual processthat relied on the doctor's skills and judgment. A number of parties arecreating and providing products and services that can be groupedtogether under the appellation ‘virtual orthodontics’. The principleelements of virtual orthodontics are representations of the teeth and oforthodontic components such as brackets and wire.

One of the values of virtual orthodontics is that the user can makechoices among available components before actually implementing thetreatment approach. For instance, an orthodontist can evaluate optionsby choosing different bracket prescriptions and features such as hooksor ligation methods before the brackets are applied to a patient'steeth.

SUMMARY

Systems and methods are disclosed for performing virtual treatment usingone or more dental appliances by receiving a digital model of a dentalappliance; selecting a standard position and orientation; and mappingthe digital model of the dental appliance to the standard position andorientation.

Advantages may include one or more of the following. The system allowsthe doctors to easily change or substitute different brackets duringtreatment planning. Thus, the doctor can simply select a differentbracket and the system automatically places the new bracket in theproper position and orientation relative to its underlying tooth. Thisis achieved by having all brackets in the same spatial coordinate systemor making use of a transform function to relate the coordinate systemsof the brackets.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an exemplary process to perform virtual treatmentusing one or more dental appliances.

FIG. 1B shows an exemplary process for substituting dental appliances.

FIG. 2 shows two different appliances, in this case brackets, in theirown virtual spaces.

FIG. 3 shows the brackets of FIG. 2, isometrically displayed in the samevirtual space.

FIG. 4 shows the substitution based on an alignment of the brackets'dimensions or features.

DESCRIPTION

FIG. 1A illustrates an exemplary process to perform virtual treatmentusing one or more dental appliances. The process includes receiving adigital model of a dental appliance (110); selecting a standard positionand orientation (120); and mapping the digital model of the dentalappliance to the standard position and orientation (130).

In one embodiment, the appliance can be a bracket. The digital model ofthe bracket can be received from a scanner or digitizer. There areseveral means of digitizing the brackets, among them computertomography, acoustic imaging, surface tracing, and destructive scanning.Any of these could be direct or indirect. The former digitizes the bodyitself. The latter digitizes an impression or a mold of the body. Thedata set produced by the 3D acquisition system may, of course, beconverted to other formats to be compatible with the software which isused for manipulating 3D images within the data set. Additionally, avariety of range acquisition systems, generally categorized by whetherthe process of acquisition requires contact with the three dimensionalobject, can be used. A contact-type range acquisition system utilizes aprobe, having multiple degrees of translational and/or rotationalfreedom. By recording the physical displacement of the probe as it isdrawn across the sample surface, a computer-readable representation ofthe sample object is made. A non-contact-type range acquisition devicecan be either a reflective-type or transmissive-type system. There are avariety of reflective systems in use. Some of these reflective systemsutilize non-optical incident energy sources such as microwave radar orsonar. Others utilize optical energy. Those non-contact-type systemsworking by reflected optical energy further contain specialinstrumentation configured to permit certain measuring techniques to beperformed (e.g., imaging radar, triangulation and interferometry).Optical, reflective, non-contact-type scanners and othernon-contact-type scanners are preferred because they are inherentlynondestructive (i.e., do not damage the sample object), are generallycharacterized by a higher capture resolution and scan a sample in arelatively short period of time. Next, a standard position andorientation is selected and the digital model of the dental appliance ismapped to the selected standard position and orientation.

A first embodiment to map appliances to the standard orientation andposition is discussed next. When the physical brackets are digitized,they are held in the same position and orientation by a jig that allowsthem to be held in the same spatial location. In one embodiment, thebracket's slot can be used to attain the same location for models withina manufacturer's line as well as across manufacturers' lines because itis one of the most consistent geometric features with the greatestdimensional similarity among all brackets.

A second embodiment to map appliances to the standard orientations andpositions is discussed below. This embodiment may be used independentlyof or in conjunction with the first embodiment discussed above. In thisembodiment, the digital representations of the brackets are opened insoftware that can read the file format(s)—it is not required that thebracket representations are in the same format. For instance, one couldbe an STL and another can be an IGES, STEP, or CAD native (e.g. Pro/E,SolidWorks, etc.) file. Next, two or more files are loaded into the samesoftware space at one time. Alternatively, each representation is loadedinto its own space and these, in turn, are loaded to a common space. Oneof the files is selected as the base bracket to determine orientationsand positions, or a separate object or coordinate system is selected asthe basis to determine bracket orientations and positions. Any otherbracket in the software space is aligned on the base bracket or thebasis using known or common dimensions and features. Examples of commondimensions and features: within some amount of tolerance, allmanufacturers' bracket slots are either 0.018″ (0.46 mm) or 0.022″ (0.56mm) in the occlusogingival direction, the slot lengths are typicallyspecified so the midpoint is easily determined, and the ‘slot point’ and‘base point’ can be identified from these two. Any other bracket issaved independently with its newly-defined position and orientation.

In the case of contralateral brackets, the steps above could be followedor a bracket can simply be mirrored relative to a reference plane orsurface to create its contralateral.

If the manufacturers' digital representations are available, the processis essentially the same as discussed above, except there is no need todigitize physical models. The positioning and orienting is less complexbecause all referents will be defined in the digital representations.

FIG. 1B shows an exemplary process for substituting dental appliances.First, an operator selects a model of a dental appliance previouslyplaced on a tooth model (150). Next, the operator selects a model of asubstitute dental appliance (160). The substitution can be based on anumber of factors including fit, height of the appliance, comfort of thepatient, or appearance of the appliance, among others. Based on theselection of the original model of the dental appliance and a substitutemodel of the appliance, the process of FIG. 1B places the substitutemodel in place of the original model of the dental appliance based onthe standard position and orientation (170)

FIG. 2 shows two different brackets in their own virtual spaces. Theircoordinate systems are different—not co-located as also can be seen bythe difference in arrow orientations shown in the bottom left corner ofeach panel.

FIG. 3 shows the same two brackets isometrically displayed in the samevirtual space. The coordinate system of the space does not coincide withthat of either bracket. It can be seen that if one bracket were toreplace the other, that the orientations, at least, would differ.

FIG. 4 shows that an alignment of the dimensions and/or features of thebrackets causes them to have shared positions and orientations. If oneis replaced with the other, these would not be changed in a virtualorthodontic setup.

The system can also be used to model the effects of more traditionalappliances such as retainers, aligners and other removable dentalappliances and therefore be used to generate optimal designs andtreatment programs for particular patients.

The model of the brackets can be displayed and manually positioned ormanipulated using a suitable dental CAD system. In this embodiment, abracket is positioned on a tooth based on a prescription. Should theuser wish to use a different bracket, the user merely selects adifferent bracket and indicates to the computer that the new bracket isto be used. The system deletes the first bracket and inserts the newbracket in the same spatial position and orientation of the originalbracket without requiring the user to manually place the new bracket atthe same location of the original bracket.

Alternatively, the system can automatically place the brackets for theuser. In either a manual or automated placement system, the commoncoordinate system allows the user to select a substitute bracket andautomatically insert the substitute bracket in place of the originalbracket. A general flow of an exemplary process for defining andgenerating repositioning appliances for orthodontic treatment of apatient is discussed next. The process includes the methods, and issuitable for the apparatus, of the present invention, as will bedescribed. The computational steps of the process are advantageouslyimplemented as computer program modules for execution on one or moreconventional digital computers.

As an initial step, a mold or a scan of a patient's teeth or mouthtissue is acquired. This generally involves taking casts of thepatient's teeth and gums, and may also involve taking wax bites, directcontact scanning, x-ray imaging, tomographic imaging, sonographicimaging, and other techniques for obtaining information about theposition and structure of the teeth, jaws, gums and otherorthodontically relevant tissue. From the data so obtained, a digitaldata set is derived that represents the initial (that is, pretreatment)arrangement of the patient's teeth and other tissues.

The initial digital data set, which may include both raw data fromscanning operations and data representing surface models derived fromthe raw data, is processed to segment the teeth into individual toothmodels for manipulation. Digital models of each tooth can be produced,including measured or extrapolated hidden surfaces and root structures.

The desired final position of the teeth—that is, the desired andintended end result of orthodontic treatment—can be received from aclinician in the form of a prescription, can be calculated from basicorthodontic principles, or can be extrapolated computationally from aclinical prescription. With a specification of the desired finalpositions of the teeth and digital representations of the teeththemselves, the final position and surface geometry of each tooth can bespecified to form a complete model of the teeth at the desired treatmentend. Generally, in this step, the position of every tooth is specified.The result of this step is a set of digital data structures thatrepresents an orthodontically correct repositioning of the modeled teethrelative to presumed-stable tissue. The teeth and tissue are bothrepresented as digital data.

Having both a beginning position and a final position for each tooth,the process next defines a tooth path for the motion of each tooth. Thetooth paths are optimized in the aggregate so that the teeth are movedin the quickest fashion with the least amount of round-tripping to bringthe teeth from their initial positions to their desired final positions.(Round-tripping is any motion of a tooth in any direction other thandirectly toward the desired final position. Round-tripping is sometimesnecessary to allow teeth to move past each other.) The tooth paths aresegmented. The segments are calculated so that each tooth's motionwithin a segment stays within threshold limits of linear and rotationaltranslation. In this way, the end points of each path segment canconstitute a clinically viable repositioning, and the aggregate ofsegment end points constitute a clinically viable sequence of toothpositions, so that moving from one point to the next in the sequencedoes not result in a collision of teeth.

The threshold limits of linear and rotational translation areinitialized, in one implementation, with default values based on thenature of the appliance to be used. More individually tailored limitvalues can be calculated using patient-specific data. The limit valuescan also be updated based on the result of an appliance-calculation,which may determine that at one or more points along one or more toothpaths, the forces that can be generated by the appliance on thethen-existing configuration of teeth and tissue is incapable ofeffecting the repositioning that is represented by one or more toothpath segments. With this information, the subprocess defining segmentedpaths can recalculate the paths or the affected subpaths.

At various stages of the process, and in particular after the segmentedpaths have been defined, the process can, and generally will, interactwith a clinician responsible for the treatment of the patient. Clinicianinteraction can be implemented using a client process programmed toreceive tooth positions and models, as well as path information from aserver computer or process in which other processes are implemented. Theclient process is advantageously programmed to allow the clinician todisplay an animation of the positions and paths and to allow theclinician to reset the final positions of one or more of the teeth andto specify constraints to be applied to the segmented paths. If theclinician makes any such changes, the subprocess of defining segmentedpaths is performed again.

The data processing aspects of the invention can be implemented indigital electronic circuitry, or in computer hardware, firmware,software, or in combinations of them. Data processing apparatus of theinvention can be implemented in a computer program product tangiblyembodied in a machine-readable storage device for execution by aprogrammable processor; and data processing method steps of theinvention can be performed by a programmable processor executing aprogram of instructions to perform functions of the invention byoperating on input data and generating output. The data processingaspects of the invention can be implemented advantageously in one ormore computer programs that are executable on a programmable systemincluding at least one programmable processor coupled to receive dataand instructions from and to transmit data and instructions to a datastorage system, at least one input device, and at least one outputdevice. Each computer program can be implemented in a high-levelprocedural or object-oriented programming language, or in assembly ormachine language, if desired; and, in any case, the language can be acompiled or interpreted language. Suitable processors include, by way ofexample, both general and special purpose microprocessors. Generally, aprocessor will receive instructions and data from a read-only memoryand/or a random access memory. Storage devices suitable for tangiblyembodying computer program instructions and data include all forms ofnonvolatile memory, including by way of example semiconductor memorydevices, such as EPROM, EEPROM, and flash memory devices; magnetic diskssuch as internal hard disks and removable disks; magneto-optical disks;and CD-ROM disks. Any of the foregoing can be supplemented by, orincorporated in, ASICs (application-specific integrated circuits).

To provide for interaction with a user, the invention can be implementedusing a computer system having a display device such as a monitor or LCD(liquid crystal display) screen for displaying information to the userand input devices by which the user can provide input to the computersystem such as a keyboard, a two-dimensional pointing device such as amouse or a trackball, or a three-dimensional pointing device such as adata glove or a gyroscopic mouse. The computer system can be programmedto provide a graphical user interface through which computer programsinteract with users. The computer system can be programmed to provide avirtual reality, three-dimensional display interface.

The invention has been described in terms of particular embodiments.Other embodiments are within the scope of the following claims. Forexample, the operations of the invention can be performed in a differentorder and still achieve desirable results.

1. A method for performing virtual treatment using one or more dentalappliances, comprising: receiving a digital model of a dental appliance;selecting a standard position and orientation for the dental appliancein relation to a tooth model; and mapping the digital model of thedental appliance to the standard position and orientation, wherein themapping comprises setting a plurality of digital models to the standardposition and orientation.
 2. The method of claim 1, comprising whereinthe mapping comprises setting a plurality of digital models to thestandard spatial position and orientation.
 3. The method of claim 1,comprising placing a digital model of a first dental appliance on thetooth model.
 4. The method of claim 3, comprising interchanging thefirst dental appliance with a second dental appliance.
 5. The method ofclaim 4, comprising automatically placing the second dental appliance atthe same position as the first dental appliance.
 6. The method of claim1, comprising scanning a dental appliance to create the digital model.7. The method of claim 1, comprising selecting a base object todetermine the standard position and orientation.
 8. The method of claim7, wherein the base object is one of the dental appliances.
 9. Themethod of claim 7, wherein the base object is a separate object.
 10. Themethod of claim 1, comprising selecting a coordinate system as the basisfor the standard position and orientation.
 11. The method of claim 1,wherein the standard position and orientation is determined usingpredetermined dimensions and features on the dental appliances.
 12. Amethod for performing virtual treatment using one or more dentalappliances, comprising: receiving a digital model of a dental appliance;selecting a standard position and orientation for the dental appliancein relation to a tooth model; and mapping the digital model of thedental appliance to the standard position and orientation; wherein thestandard position and orientation is determined using predetermineddimensions and features on the dental appliances.
 13. The method ofclaim 12, wherein the slot comprises an 0.018″ (0.46 mm) or 0.022″ (0.56mm) width channel running in a mesiodistal direction.
 14. The method ofclaim 12, wherein one dimension comprises a slot length.
 15. The methodof claim 12, wherein one dimension comprises a slot point.
 16. Themethod of claim 12, wherein one dimension comprises a base point. 17.The method of claim 1, comprising associating the digital model of theappliance with reference to the standard position and orientation. 18.The method of claim 1, wherein the dental appliance is a bracket.
 19. Amethod for performing virtual treatment using one or more dentalappliances, comprising: receiving a digital model of a dental appliance;selecting a standard position and orientation for the dental appliancein relation to a tooth model; and mapping the digital model of thedental appliance to the standard position and orientation; wherein thedental appliance is a bracket.
 20. The method of claim 1, comprisinginterchanging the dental appliances in accordance with specifiedcriteria.
 21. A method for performing virtual treatment using one ormore dental appliances, comprising: receiving a first digital model of adental appliance and a second digital model of a dental appliance;selecting a standard position and orientation for the first dentalappliance in relation to a tooth model; mapping the first digital modelof the dental appliance to the standard position and orientation;mapping the second digital model of the dental appliance to the standardposition and orientation digitally placing the first digital model inconjunction with a digital representation of a tooth or an orthodonticappliance: and interchanging the second dental appliance with the firstdental appliance.
 22. The method of claim 1, comprising mapping an axisdirection for the digital model.
 23. The method of claim 1, comprisinggenerating a template to place the dental appliance on a tooth.
 24. Amethod for performing; virtual treatment using one or more dentalappliances, comprising; receiving a digital model of a dental appliance;selecting a standard position and orientation for the dental appliancein relation to a tooth model; mapping the digital model of the dentalappliance to the standard position and orientation: and generating atemplate to place the dental appliance on a tooth.
 25. A method for usein virtual treatment of teeth using appliances, comprising: providing adigital model of each of a plurality of different dental appliances; andmapping the digital models of the different dental appliances based onat least one common feature element of each dental appliance so thateach of the digital models of the different dental appliances, oncepositioned in relation to a digital representation of a tooth or otherdental appliance, can be respectively replaced, by reference to thecommon feature element, by a different digital model that will bepositioned in the same spatial position and orientation as the originaldigital model.
 26. The method of claim 25, wherein: the digital modelsare mapped based on at least one common feature element of each dentalappliance and an orientation in a three-dimensional coordinate system.27. The method of claim 26, wherein: the digital model is replaced byreference to the common feature element and the orientation of thedental appliances in the three-dimensional coordinate system.
 28. Amethod for use in virtual treatment of teeth using appliances,comprising: providing a digital model of each of a plurality ofdifferent dental appliances; mapping the digital models of the differentdental appliances based on at least one common feature element of eachdental appliance; digitally placing a first one of the digital models inconjunction with a digital representation of a tooth or an orthodonticappliance; and replacing the first digital model with a second digitalmodel.
 29. The method of claim 28, wherein: the replacing step comprisesplacing the second digital model by reference to the at least one commonfeature element of each dental appliance so that the second digitalmodel is positioned in the same spatial position and orientation of thefirst digital model in relation to the digital representation of thetooth or orthodontic appliance.
 30. The method of claim 29, wherein: thereplacing step comprises placing the second digital model by referenceto the at least one common feature element of each dental appliance sothat the second digital mode 1 is positioned in the same spatialposition and orientation of the first digital model in relation to thedigital representation of the tooth or orthodontic appliance and anorientation in a three-dimensional coordinate system.